6 EMC, EARTHING AND SCREENING
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Statutory Documents - IMO Publications and Documents - Circulars - Radiocommunication and Search and Rescue - COMSAR/Circ.32 - Harmonization of GMDSS Requirements for Radio Installations on Board SOLAS Ships - (16 August 2004) - Annex - Guidelines for the Harmonization of GMDSS Requirements for Radio Installations on Board SOLAS Ships - 6 EMC, EARTHING AND SCREENING

6 EMC, EARTHING AND SCREENING

 6.1 Electromagnetic Compatibility (EMC)

6.1.1 General

All reasonable and practical steps should be taken to ensure EMC compatibility between the equipment concerned and other radio communication and navigational equipment carried on board in compliance with the relevant requirements of chapters IV and V of the SOLAS Convention, as amended. In order to avoid interference the following rules applies:

  • .1 Radio installations should not cause harmful interference to other electronic, electrical or navigational systems on board ships.

  • .2 However, other systems should not cause harmful interference to the radio installation.

  • .3 In order to avoid electromagnetic noise interference it is essential that manufacturers guidelines relating to EMC, screening and earthing are correctly followed.

(SOLAS 1974, as amended, regulations IV/6.2.1 and V/17 and IMO resolutions A.694(17) and A.813(19))

6.1.2 Voluntary radio equipment

Additional, voluntarily carried non-GMDSS radio equipment may be as follows:

  • - mobile telephone;

  • - radio amateur stations; and

  • - satellite stations.

Operation of such equipment is at the discretion of the master. It may be installed on the bridge provided that the EMC requirements are fulfilled and navigation and radio communication is not degraded.

 6.2 Screening of cables

In order to avoid interference the following guidelines should apply with regards to screening of cables:

  • .1 Coaxial down leads should be used for all receiving antennas and the coax screen should be connected to ground on at least one end.

  • .2 All cables within a distance of 2 metres from a transmitting antenna should be screened and the screen properly earthed in a metal tube or duct.

 6.3 Earthing

Earthing of radio equipment should be carried out in accordance with appropriate guidelines for Earthing in Maritime Installations required in international standards. Great care should be taken in order to fulfil the following rules:

  • .1 Each unit of radio equipment should have a separated earth connection.

  • .2 MF/HF antenna tuners should be earthed with either a copper bar or copper band.

  • .3 The earthing bar or strap should be as short as possible, should not be more than one metre in length, and should be at least 60 mm in width.

  • .4 For earthing straps up to 5 metres in length the width should be at least 100 mm (May be relevant on board vessels made of wood or synthetic materials).

  • .5 It should be noted that a long earthing strap or bar will act as an antenna and radiate energy.

  • .6 Copper bars and straps should be brazed to the steel bulkhead in order to eliminate corrosion and vibration and make a good earth connection.

  • .7 Great care should be taken when earthing radio equipment on ships with aluminium superstructures in order to avoid galvanic corrosion. An approved and acceptable method of earthing should be used on such ships.

Note: - Insufficient earthing of the power amplifier may lead to capacitive and inductive connections between power cables etc. and cause interference to fire alarms, navigational equipment, inter-communication and other equipment. The transmitter output power may also be reduced.

Parent topic: Annex - Guidelines for the Harmonization of GMDSS Requirements for Radio Installations on Board SOLAS Ships
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